FUNCTIONAL EXAMINATION OF THE EAR
is a simple practical method of testing a patient's ability to understand speech
which is the function of hearing most important to most people.
Tuning Fork Tests
Tuning fork tests provide the most reliable method of determining whether
deafness is of conductive or sensorineural type. The tuning fork used should
be large so that its rate of decay is not rapid and its frequency should be
Fig. 145. Barany's noise apparatus.
Fig. 146. Testing with tuning fork by air
either 256 or 512 cycles per second. It should have an expanded base for
application to the skull. The tuning fork is struck against a resilient surface
and then held so that the acoustic axis is in line with the external acoustic
meatus (Fig. 146). In this way the sound of the fork is heard by air conduction.
If the vibrating tuning fork is held with its base held firmly against the skull
the sound is transmitted through the bones of the skull to the cochlea and
the sound of the fork is heard by bone conduction.
Air conduction in which the sound of the tuning fork is transmitted through
the normal sound-conducting pathway is much more efficient than bone
conduction in which the sound is transmitted through the bones of the skull
to the cochlea. In Rinne's test air condrrtirrn fo tpAtp.d The tuning fork still
vibrating is then applied with its base to the mastoid process and the patient
is asked which he hears louder. If the sound-conducting patkwayJ^
tuning fork is heard mjichjquder by,air conduction than by bone conduction
and Rhine's Test is said to be positive. .If the sound-conducting pathway is"